In my experience, you should highkey prioritize getting at least two extra Canon LP-E6NH Rechargeable Lithium-Ion Battery packs because that 4K video is a total battery hog, especially if youre using the EVF a lot. For storage, I’ve found that a ProGrade Digital 128GB UHS-II SDXC V60 works perfectly for the R6II's 4K bitrates without needing to drop the massive cash on V90s... unless youre doing heavy ALL-I filming all the time? Idk, V60 is usually the sweet spot for travel. Also, definitely check out the Peak Design Everyday Sling 6L for a bag. It basically fits the body and a lens like a glove and stays super slim against ur body while trekking. Seriously such a solid setup, youre gonna love it!

Like someone mentioned, V60 cards are the standard advice, but honestly? I'm gonna have to disagree slightly if you're doing anything high-speed! If you're using that 40fps electronic shutter or the 4K 60p uncropped video, V60 can actually bottleneck you. I love the R6II because it's so fast, so why slow it down? For absolute reliability and zero buffer lag, I'd go V90 for your main slot.

• Card: Kingston Canvas React Plus 128GB UHS-II SDXC V90. It's legit one of the fastest cards out there and way cheaper than the Sony alternatives.
• Power: SmallRig LP-E6NH USB-C Rechargeable Camera Battery. These are amazing because you can plug a USB-C cable directly into the battery itself. No bulky wall charger needed in your suitcase!
• Bag: Wandrd Rogue 6L Sling. It's super rugged and has this awesome expandable bottom for a tripod or water bottle. tbh I'd rather spend a bit more on the card now than miss a shot because the buffer is still clearing... enjoy the new rig, it's a fantastic camera!

tbh I’m a bit more cautious than the others here. I get the urge to save money, but I’m always worried about third-party batteries failing or swelling in a nice new camera. I’d stay with the official Canon ones just to be safe. For storage, since you're traveling, you might want to compare these two:

• Sony SF-M Series Tough 128GB UHS-II V60: It’s basically indestructible and waterproof. If you're hiking or near water, this is the way to go for reliability.
• Lexar Professional 1667x 128GB SDXC UHS-II: Much more budget-friendly and works fine for 4K clips, but the physical build isn't as solid as the Sony. As for a bag, the slings mentioned are nice, but I prefer something like the Think Tank Photo Mirrorless Mover 20. It's super slim but has way more protective padding than most fashion-focused slings. It fits the R6 II like a glove and I don't have to worry about it getting bumped around. Just feels a bit more secure for a beginner like me who is paranoid about scratches...

Honestly, I totally agree about the V60 cards being the sweet spot for travel. You're gonna save a ton of money over V90s, and for most 4K clips, you basically won't even notice a difference in performance. I’ve been using SanDisk 128GB Extreme PRO UHS-II SDXC cards and they’re super reliable without that massive price hike. One thing I’d add to the power situation: if you wanna stay budget-conscious, instead of buying four or five OEM batteries, look into a solid power bank with Power Delivery (PD). I use an Anker 737 Power Bank (PowerCore 24K) and it’s a lifesaver. You can charge the R6II directly via USB-C while you're grabbing lunch or sitting on a train, which is pretty much essential if you’re shooting video all day. Just make sure your cable is rated for PD too! For a bag, if you want something that doesn't scream 'expensive camera' to everyone on the street, the Bellroy Venture Sling 6L is a great alternative. It’s pretty slim and fits the body plus a 24-105mm comfortably. Also, maybe grab a cheap tempered glass screen protector? It's like ten bucks but keeps that articulating screen mint while it's bumping around in your bag.